AEW Radar Concepts

Many radar systems need to be able to accurately determine a target's height above terrain. In airborne early warning (AEW) systems, the radar antenna is limited in its vertical aperture, thus producing a broad beamwidth in elevation. This reduces its curacy for height fmding. An alternate method of height fmding is to measure the delay of a ground-bounce (multipath) signal from the target, referenced to the direct line of sight path. This has been demonstrated successfully with AEW radars which operate over water in certain situations, but has had limited success over land. The problem has been the lack of an accurate, robust signal processing algorithm for determining the time delay between closely spaced direct and ground bounce returns. Our basic objective was to make credible the premise that an airborne AEW radar can accurately determine height of targets by processing the delayed echo due to the multipath ground bounce. Current AEW systems use this technique, but in a limited way -usually only over water, where the surface reflection is strong and predictable and when it is well separated from the direct reflection. It has been recognized for some time that land also can cause multipath reflections, but due to its irregular nature, this technique has not been exploited thoroughly. Therefore, our objectives were to show height finding can be done accurately when the direct pulse overlaps the specular return (over water or land). The signal processing problem is essentially one of performing time-of-arrival estimation of two or more pulse returns; the direct plus one or more ground bounce echoes. For typical AEW scenarios, the echoes may overlap the direct return and are usually of lower amplitude. Therefore, the algorithm must make use of the maximum information content of the signal and should have as low a threshold signal to noise ratio as possible in order to apply in the greatest number of conditions. This problem will also occur in laser radar systems, and has an exact analog for the phased-array direcfion-of-arrival estimation. The signal processing results of this paper can be applied to pulsed or frequency modulated continuous wave radar/ladar systems. We assume that the target has been detected and that it is of interest to estimate the target's height above terrain. This processing would occur at baseband using a complex demodulated channel. In general, some form of averaging is often used to enhance the SNR of small signals, such as Doppler processing (the technique is described later in this paper) and the algorithms are shown to be compatible with these operations. The algorithm could be used in some situations for enhanced detection as well. Using knowledge of the terrain, the surveillance aircraft altitude and the time delay estimates of the echoes, we can infer target height. Concurrent with the basic objective, we gathered an extensive, fairly high-resolution data set of the surface reflection of various terrain types at two radar hand frequencies: 430 MHz (UHF) and 1255 MHz (L-band). Data were to be collected for each polarization: horizonial, vertical, and cross-polarization. The main terrain of interest was rugged terrain; the predominant view being that the echo data taken in very rugged terrain would be the most difficult to extract. Calibration data were collected over water, and much data of fairly flat, predictable terrain were also taken.

Early warning radar is able to effectively detect the target utilizing Doppler Effects between the target and radar. The detection effectiveness of the airborne early warning radar is affected by its detection range as well as its detection probability. In this paper, a method for simulating the detection effectiveness of the airborne early warning radar is proposed. First, the detection model of the airborne early warning radar is designed. And then, based on the motion parameters of the airplane and target as well as the radar system parameter, the detection effectiveness of the early warning radar is simulated and displayed dynamically. Finally, the detection effectiveness of the early warning radar is validated. Simulation results show that the proposed method can effectively simulate the detection effectiveness of the airborne early warning radar, and has the friendly man-machine conversation.

The space-time adaptive processing (STAP) can improve the performance of airborne early warning (AEW) radar. But, the receiver channel mismatch will give rise to much degradation of the performance for STAP. This paper introduces an efficient adaptive channel equalization method which can compensate the channel mismatch automatically by least squares theory. The effect of equalizer parameters on equalization performance is analysed in detail, and a sample of adaptive channel equalizer is given.

FREDI: Robust RSS-based ranging with multipath effect and radio interference

MQRP: Mobile sinks-based QoS-aware data gathering protocol for wireless sensor networks-based smart grid applications in the context of industry 4.0-based on internet of things

The visible light communication (VLC) technology based on the lighting system of space station is put forward. The VLC has advantages of not taking up radio spectrum, no electromagnet interference and radiation, high emission power and good secrecy. This paper mainly studies to improve inter-symbol interference and fading problem caused by multipath effects in VLC system using RAKE receiving technology. The simulation results in this paper indicate that optical receiving technology utilizing RAKE can not only resolve the inter-symbol interference and reduce the bit error rate (BER), but also improve the signal to noise ratio of the system output.

The microburst prediction radar is a new low cost airport weather surveillance radar. Intended for on-airport siting, the X-band radar features small size and low radiated power. The system provides 2-4 minutes warning and continuous detection of hazardous microburst wind shear within a 10 km radius. System cost is $500-700K, including installation.

The biggest problems of online monitoring stress for crane currently are the signal stability problem and the high cost problem. Aiming at these problems, the authors design the stability monitoring project for shipbuilding portal crane. The project adopts the wired monitoring method and the strain signal is amplified preliminarily at the measuring point, the combination of both which overcomes the problems of strain signal attenuation and electromagnetic interferences. The acquisition box is reset punctually to avoid the drift problem. An experiment of online monitoring stress for shipbuilding portal crane used for 5 years is done in a shipyard, and the experiment proves that the effective relative error is less than 6%. Compared with the wireless monitoring way, the project costs lower and isnt subject to electromagnetic interferences. Moreover, compared with the traditional wired monitoring way, the program has more stability signal.

The Global Navigation Satellite System (GNSS) is an important tool that is vulnerable to both intentional and unintentional radio frequency interference (RFI). This work seeks to develop a low-cost GNSS RFI monitor to detect and classify interference in an area. We present multiple signal combination-based jamming and spoofing experiments and provide an analysis of the results. Several simulated short duration jamming tests are applied to both L1 and L2 signals with four types of jamming interference, including continuous wave, narrowband jamming; broadband, additive white Gaussian noise jamming; chirp interference; and pulsed-chirp interference. A lift-off spoofing experiment combines real-time GNSS signals using two receive-only antennas and a programmable attenuator. The signals are processed using a low-cost u-blox F9P receiver and various power and signal quality metrics are analyzed. Specifically, the carrier-to-noise ratio (C/N0), the automatic gain control (AGC), and spectral analyses are useful for both identifying interference and classifying types of interference. Differences in power metric responses are observed depending on the characteristics and waveform of the jamming interference. Analyzing the position solution in addition to power metric and signal quality monitoring is found to be especially insightful in detecting the presented spoofing scenario. Our results characterize how the u-blox F9P receiver measures the several types of RFI and show the advantages of monitoring multiple metrics when monitoring for interference.

Space-time adaptive processing (STAP) is the key technology of airborne early-warning radar to suppress both clutter and interference, and the extended factored approach (EFA) is the well-established reduced-dimension (RD) STAP approach for engineering implementation. In this paper, the adaptive monopulse technique is introduced into EFA, and an efficient space-time adaptive monopulse to jointly estimate the target velocity and location is presented. Theoretical analysis and simulation results demonstrate that, when the real target Doppler frequency deviates from the central frequency of the Doppler bin, the proposed approach can estimate the velocity and angle parameters more precisely than the conventional adaptive monopulse.

Radar systems play a crucial role in target tracking within urban environments, where challenges such as clutter, multipath effects, and electromagnetic interference significantly impact detection accuracy. Traditional radar methods often struggle to adapt to dynamic urban conditions, leading to decreased reliability in real-time target tracking. This study aims to develop and evaluate an AI-driven adaptive radar system that enhances tracking accuracy in urban settings. The research employs a quantitative approach using simulations to model radar signal processing under various environmental conditions. The AI model, based on Convolutional Neural Networks (CNN), is trained to optimize radar performance by filtering out noise and dynamically adjusting detection parameters. The results indicate that the AI-based radar system achieves a tracking accuracy of 95.2%, significantly outperforming traditional radar systems, which only reach 80% accuracy. Additionally, the AI-enhanced radar reduces response time to 120 milliseconds, compared to 250 milliseconds in conventional systems, demonstrating improved real-time processing capabilities. The system also exhibits greater resilience to high-clutter environments, maintaining stable target detection despite signal interference. These findings highlight the potential of AI in enhancing radar functionality for applications such as surveillance, traffic monitoring, and security. Future research should focus on integrating AI-driven radar with real-world radar hardware, exploring multi-sensor fusion, and refining adaptive learning techniques to further optimize tracking performance in complex environments

TEQC is a tool which can be commonly used in GNSS data translation, editing, and quality checking, it's widely used in GNSS data preprocessing. This paper has introduced the common syntax and instruction of TEQC when it used in GNSS data processing, also introduced the testing examples of GNSS receiver under three environments: 220KV UHV transmission line environment, 500KV UHV transmission line environment and standard GNSS calibration field, then using TEQC to preprocess and analysis the data. The results showed that: a)The GNSS observation data Efficiency is not effected from radio interference generated by EHV transmission lines; b)Within 25 meters ranges GNSS observation data under EHV transmission line, the multi-path effects (mp1 and mp2 value) significantly exceeded the normal range, and the voltage higher, the multi-path value larger. c)Apart from 50 meters outside EHV transmission line, there is almost no effect about multi-path affects in the high-precision GNSS observation data.

Under the complex operational environment of the antimissile operation, the application of Systems Modeling Language (SysML) parametric model in weapon system effectiveness evaluation is explored. The function of parametric graph model, the construction process of the model and the optimization method of the model are researched. Using feedback mechanism to collect, collate and calculate the parameters of the model, and realize the leap from the index relationship description to the calculation of the index. Finally, the feasibility and effectiveness of the proposed method is verified by using the system of antimissile weapon system as an example.

The accomplishments of the Signal Corps Laboratories in the development of radar are described with emphasis on the pre-World War II period. The development and evolution of early warning radar and fire control radar in the Army are treated in some detail. The ground radars used in combat during the war by the Army (including the Army Air Corps) are discussed.

The ground and sea clutter received by space-based early warning radar (SBEWR) has severely range ambiguous characteristics due to its platform location, and the non-stationary factor caused by Earth’s rotation makes the received clutter at different range ambiguous positions seriously broaden in the Doppler dimension. The complex clutter suppression performance of SBEWR obtained by traditional method is degraded significantly. To solve this problem and achieve better clutter suppression performance, a novel multi-domain adaptive processing method for clutter suppression is proposed in this paper. The proposed method introduced a range related signal processing domain based on conventional space–time domain by using frequency diverse array phase multiple-input multiple-output (FDA-Phase-MIMO) radar. In addition, a novel multi-domain joint dimensionality reduction structure was designed. The novel multi-domain joint adaptive processing using the proposed dimensionality reduction structure could not only obtain great clutter suppression performance of SBEWR, but also minimize the requirement of the number of selected auxiliary channels. Simulation examples show the effectiveness of the proposed method.